1. Field of the Invention
The invention relates to a zoom lens comprising in a direction of light propagation a front lens group having positive refractive power, a variator lens group having negative refractive power, a compensator lens group having positive refractive power, a base lens group having positive refractive power.
Numerous zoom lenses are already known from the prior art. The zoom lenses must fulfil specific optical and/or mechanical properties, depending on requirement.
2. Description of the Related Art
Zoom objectives for photography typically have a zoom factor of 2 to 4. The exit pupil vision is not telecentrically configured here. The installed length is to be kept as short as possible with these zoom lenses.
Furthermore, zoom lenses for video recordings, for example camcorders, are known from the general prior art. The CCD detectors used in this case have an image diameter of at most 11 mm. The zoom factor is specified here mostly as 10, the focal range reaching from 3 mm to 50 mm in known makes.
The zoom factor for such lenses is approximately 20 to 30 in the case of zoom lenses for television recordings. The CCD detectors used in this case have an image diameter of typically 11 mm. Focusing is performed here by the front group, as a rule. These lenses must have a long back focus in order to be able to install a color-splitting prism between a last lens and a detector.
Afocal zoom lenses are frequently used as component parts in instrumental optics. The diaphragm position can be varied during the zooming operation in the case of such systems.
None of the zoom lenses enumerated corresponds per se to the desired characteristics of a zoom lens for military reconnaissance. It is also impossible to create other characteristics for the said zoom lenses by a few and simple conversions by means of known optical computing programs. Moreover, the multiplicity of afocal zoom lenses have a smaller diameter to achieve a constant aperture number over a focal range of up to approximately 280 mm in combination with a lens of suitable focal length.